The sealant spray gun calibration is an integral part of robotic sealant applications.
In a typical robotic sealant system objects to be sealed are the spot welded seams of cars that have been primer-coated. Panels of the car are thin sheet metal stamped for reinforcement and the edges of these panels have burrs from the shearing operation; in addition, there are small concaves and distortions around the seams due to spot welding.
As a result, the seams become irregular lines. To effectively seal the seams with an economical amount of sealing material, the spray gun must accurately track the complex seams during the sealing operation. To obtain this accuracy the working tool center point of the spray stream must be fixed in space (calibrated) prior to path teaching (programming) the robot.
To maintain accuracy, the sealant gun has to be adjusted every once in a while because of the following reasons: the wear of the gun nozzle; robot collision causing distortion of gun, nozzle, etc.; and change of nozzle angle after the replacement of the gun or nozzle.
The conventional calibration method is to adjust gun orientation by moving the robot or the gun on its mounting. Although this method can adjust the position and orientation of the gun, it is very difficult to predict the direction of the sealant stream.
Also, the space in which the robot arm works may be severely restricted so that no alteration of the robot arm programmed path may be tolerated.